How to calculate the weight of aluminum coil?

The aluminum coil is different from the aluminum plate.

The aluminum coil is cylindrical, while the aluminum plate is square. Knowing that the length, width and thickness can be calculated in the form of weight = density * volume.
The calculation of the aluminum coil needs to know the coil diameter, width, and outer diameter of the coil core. By calculating the overall weight and subtracting the blank part of the middle coil hole, the actual value is obtained.
Aluminum coil weight.

The so-called calculation formula is: π(roll diameter/2-roll core outer diameter/2)²*width;π(OD/2-ID/2)² *width 

For example, the diameter of the 1050 aluminum coil is 103mm, the width is 300mm, and the outer diameter of the coil core is 76mm. By calculating the weight of this small coil is 3Kg.